There are known in the art a plurality of commercially available vibratory conveyor systems for controlling the speed and direction of articles or materials being conveyed thereby. Many prior art systems vary conveying speed and direction by changing either the direction or magnitude of a force applied to a conveyor trough that is resiliently mounted on a suspension system to permit vibratory motion to be imparted thereto. Alternative prior art conveying systems employ a wide variety mechanical systems to elevate or decline an end of the vibratory conveyor, thereby changing the angle of inclination of the entire conveyor trough to speed up or slow down the progress of an article along the conveyor.
One exemplary prior art system of this nature is U.S. Pat. No. 5,615,763 to Schieber, assigned to Carrier Vibrating Equipment, Inc., of Louisville, Ky., herein incorporated by reference. Generally speaking, this systems varies the vibratory force being applied to a resiliently mounted conveyor trough by securing to the trough a plurality of shafts having a plurality of eccentric weights mounted thereto. The shafts, and consequently the eccentric weights, are capable of rotation, typically through the action of driven pulleys or the like such that the rotating shafts and eccentric weights impart a vibratory force to the conveyor trough.
The angle of the vibrating force acting on the conveyor in such systems is determined by the relative position of the eccentric weights on the rotating shafts. The relative position, or phase angle relationship between eccentric weights may be maintained and controlled by various mechanical control and positioning systems or alternatively, by utilizing an electronic control system to monitor and adjust the phase angle relationships between various rotating masses.
Prior art vibratory conveyor systems are incapable of monitoring an article being conveyed to adjust the speed and direction of conveyance to impart a desired amount of vibratory force to an article before its discharge from the conveyor. The ability to monitor an article's position or progress along the conveyor can be very beneficial for certain products and manufacturing processes that require the input of a particular amount of force over a given time period for proper production. For example, some casting and molding processes utilize vibratory force to separate a casting or part from its mold and concomitant media. In many prior art systems, foundries utilize vibratory shakeout devices to mechanically separate sand or other surrounding media used in the casting process from the casting itself.
In operation, prior art vibratory shakeout devices have attempted to control the time a casting is retained in its mold by changing the elevation of one end of the shakeout to change the angle of inclination of the conveyor trough. Longer casting retention times are typically required for more complete media removal whereas short retention times are desirable for more fragile castings since a shorter retention time typically requires that less vibratory force is imparted through the conveyor trough to the fragile casting. Increasing the angle of inclination of a shakeout typically increases the retention time of a casting in the mold and, conversely, decreasing shakeout inclination usually decreases mold retention time.
Many prior art shakeout systems utilizing angle of inclination type control systems are relatively unreliable since they typically employ complex mechanical systems such as air bellows or hydraulic cylinders to elevate an end of the shakeout. These mechanical systems are inherently unreliable, particularly in the harsh industrial environment of a foundry or other molding facility. Furthermore, many prior art systems offer only a limited range of process control since the angle of inclination can only be raised a few degrees before the ability to convey the casting forward along the conveyor trough ceases unless a tremendous amount of vibratory force is applied. Additionally, variations in casting speed are difficult to effect with these prior art systems.